An US Senator's term of office is six years while a Representative's term is only two years. So there will be three elections for Representative while just once for Senator.
I am not sure which situation you are referring to, but the role of a senator tends to be larger than that of a representative, which might be why it takes longer to elect a senator.
The Communist Manifesto written by Karl Marx and Friedrich Engels is considered one of the founding documents of communist thinking and the communist political movement.
